1. Field of the Invention
The present invention relates to a thrust stopper for a camshaft in a cylinder head arrangement for an internal combustion engine. In particular, the present invention is directed to a thrust stopper that is fixed within the cylinder head arrangement to secure a camshaft within the cylinder head housing against axial movement and lateral movement. The thrust stopper in accordance with the present invention ensures that the valve operating assembly is positioned correctly within the cylinder head arrangement.
2. Description of Related Art
JP 09-144 512 A describes a cylinder head with a camshaft and a rocker arm shaft to actuate inlet and exhaust valves, in which the camshaft is secured in the axial direction by two thrust stoppers. Each thrust stopper functions as an axial stop for the camshaft in one direction. The thrust stoppers, which are in the form of sheet metal parts, are secured to the cylinder head arrangement using bolts. This thrust stopper requires multiple installation steps and the use of fasteners, which increases costs and assembly time.
A similar method for securing the camshaft has been used by the assignee of the present invention in scooter motors for a number of years. In this instance, the thrust stopper is also of sheet metal and is secured using bolts to one end face of the cylinder head. In contrast to JP 09-144 512 A, however, the sheet metal part engages in a slot-like recess in the camshaft, and this ensures axial retention in both directions. Thus, only one thrust stopper is required. The slot-like recess or groove is positioned between a camshaft drive assembly and the cam lobes and thus reduces the cross section of the camshaft, which could weaken the camshaft.
Austrian Reference No. AT 3.202 U1 describes a cylinder head with a camshaft and a rocker arm shaft. A positioning device is provided to ensure that the rocker arm shaft is positioned correctly. The positioning device includes a plug that is fixed in a receiving opening in the rocker arm shaft. The plug has a projection formed as a ridge that fits in a groove in the end of the rocker arm shaft. This ensures the rapid and correct positioning of the rocker arm shaft, although the rocker arm shaft can be installed in two positions that are rotated through 180 degrees relative to each other. This positioning device, however, is inadequate for rocker arm shafts that can be used only in one single position.
It is an object of the present invention to provide a thrust stopper for securing a camshaft in a proper orientation within a cylinder head arrangement within an internal combustion engine.
It is another object of the present invention to provide a thrust stopper that prevents axial movement of the camshaft within the cylinder head arrangement.
It is another object of the present invention to provide a thrust stopper for securing the camshaft within the cylinder head arrangement using limited parts and reduced assembly time.
It is another object of the present invention to provide a thrust stopper for securing a valve operating assembly in a proper orientation within the cylinder head arrangement.
It is another object of the present invention to provide a thrust stopper for securing both a camshaft and valve operating assembly in proper orientations within the cylinder head arrangement.
It is another object of the present invention to provide a thrust stopper that may be installed within a cylinder head housing without the use of fasteners.
It is another object of the present invention to provide a thrust stopper that is installed within a cylinder head housing and does not clatter within the housing.
It is another object of the present invention to provide a thrust stopper for securing both a camshaft and a pair of valve operating assemblies in proper orientations within the cylinder head arrangement.
It is yet another object of the present invention to provide a common thrust stopper design that is capable of being used in various engines and engine configurations.
In response to the foregoing challenges, applicants have developed a thrust stopper for use in a cylinder head arrangement of an internal combustion engine to retain a camshaft in a desired orientation while preventing axial movement of the same. The thrust stopper is configured essentially as a lock that is inserted into a receiving opening or recess in the cylinder head housing. It is contemplated that the thrust stopper can be used for different types of engines. Once the camshaft has been slid into a receiving bore in the cylinder head housing, the camshaft can be secured axially by inserting the thrust stopper into the receiving opening in the cylinder head housing. In order to simplify removal of the thrust stopper from the receiving opening, the receiving opening may incorporate a dismantling recess.
In accordance with the present invention, the thrust stopper includes a first orienting assembly for orienting the camshaft in a predetermined camshaft orientation within the cylinder head housing. The first orienting assembly includes a retaining section formed in the thrust stopper. The retaining section is sized to be received within a groove formed in an outer surface of the camshaft. The groove in the camshaft is located adjacent an end of the camshaft that is opposite to the camshaft drive assembly. The retaining section may have a reduced cross section or thickness with respect to the remainder of the thrust stopper. The retaining section is preferably assymetrically disposed with respect to a vertical mid-plane extending through the thrust stopper.
In accordance with the present invention, the thrust stopper includes a recess located adjacent the retaining section. The recess has a shape that corresponds to the cross section of the outer diameter of the camshaft. The location of the retaining section and the recess on the lower end of the thrust stopper permits the thrust stopper to be inserted into the cylinder head housing in only one orientation. This arrangement ensures that the thrust stopper and in particular the second orienting assembly, described below, is properly oriented. It is preferable that the retaining section is located on one side of the vertical mid-plane and the recess is located on an opposite side of the vertical mid-plane.
As discussed above, the retaining section fits in an annular groove in the camshaft to form an interlocking connection. The side surfaces of the retaining section of the first orienting assembly also serve as an axial bearing for the camshaft. The thrust stopper, and in particular, the retaining section of the first orienting assembly has a plate-like shape. Consequently, the receiving opening is preferably formed as a slot. The plate-like shape permits the retaining section of the thrust stopper to rest against the side surfaces of the annular groove over a relatively large area, which reduces wear. In order to absorb the considerable mechanical stresses in the area of the first orienting assembly, it is preferred that the thrust stopper be formed of a sintered metal.
To save space, the thrust stopper may be arranged in the cylinder head housing at an end of the camshaft that is remote from the camshaft drive system. The thrust stopper can be held captive by a rocker arm shaft and/or by a valve cover on the cylinder head housing. This prevents movement of the thrust stopper in the receiving opening. In some instances, the rocker arm shaft is positioned within the cylinder head housing such that rocker arm shaft secures the thrust stopper within the receiving opening in the cylinder head housing whereby a portion of the rocker arm shaft extends over the thrust stopper. No additional fasteners are needed to fix the thrust stopper in place within the cylinder head housing.
In accordance with the present invention, the thrust stopper may further include a breather channel formed therein. The breather channel forms a passageway from the recess in the thrust stopper adjacent the retaining section to prevent a pressure build up within the cylinder head housing adjacent the end face of the camshaft to avoid the buildup of pressure, which may create an axial froce against the end of the camshaft.
The thrust stopper is offset slightly from the camshaft in the radial direction so that there is no contact between the face surface of the thrust stopper and the cylindrical outside surface of the camshaft. A slight clearance is present between these components. The supporting surfaces of the thrust stopper, which are preferably arranged parallel to the axis of the camshaft, lie on corresponding fixed shoulders of the cylinder head housing, on opposing sides of the camshaft.
It is particularly advantageous if the thrust stopper is configured as a positioning device used to ensure that a valve operating assembly is positioned correctly along with the adjacent camshaft. In accordance with the present invention, the thrust stopper further includes a second orienting assembly for orienting the valve operating assembly in a predetermined operating position within the cylinder head housing. When the valve operating assembly includes a rocker arm shaft, the second orienting assembly is adapted to engage an end portion of the rocker arm shaft to maintain it in a predetermined rocker arm shaft orientation within the cylinder head housing.
It is contemplated that the first orienting assembly is located on one end or bottom side of the thrust stopper and the second orienting assembly is located on an opposite end or top side of the thrust stopper. The present invention, however, is not limited to such an arrangement; rather, it is contemplated that the first and/or second orienting assemblies may be located between the top and bottom sides of the thrust stopper.
In accordance with the present invention, the retaining section of the first orienting assembly and the second orienting assembly are located on the same side of the vertical mid-plane. Although it is not preferred, the retaining section and the second orienting assembly may be located on opposing sides of the vertical mid-plane. It is also contemplated that the first orienting assembly may include a second recess such that a first recess is positioned on one side of the retaining section and a second recess is positioned on an opposite side of the retaining section.
In accordance with the present invention, the second orienting assembly may include at least one interlocking assembly, wherein the interlocking assembly engages a portion of the valve operating assembly to create an interlocking connection between the thrust stopper and the valve operating assembly. The interlocking connection ensures that the valve operating assembly can only be installed in one predetermined position. This is especially important when the valve operating assembly, particularly the rocker arm shaft, is hollow and incorporates oil supply ports. Incorrect positioning of the oil supply ports may adversely impact the engine""s lubrication system.
The interlocking assembly may include at least one projection. Each projection may take the form of a rib extending from a surface of the thrust stopper. The rib is adapted to be received within a recess within the rocker arm shaft. Alternatively, the rocker arm shaft may include a projection that is received within a recess in the thrust stopper.
It is contemplated that the thrust stopper in accordance with the present invention may be used in various types of engines. The number of cylinders in the engine may vary, the orientation of the cylinders may vary, and the configuration of the valve operating assemblies may vary. With this in mind, the interlocking assembly preferably includes a pair of projections.
The thrust stopper in accordance with the present invention may be used in an engine having a pair of rocker arm shafts containing rocker arms thereon that are driven by the cams on a common camshaft. The rocker arms positioned on one rocker arm shaft control the operation of the valves associated with the engine exhaust. The rocker arms positioned on the other rocker arm shaft control the operation of the valves associated with the engine intake. With this arrangement, a first rocker arm shaft engages one of the projections of the second orienting assembly and a second rocker arm shaft engages another projection spaced from the first rib.
The same thrust stopper design (with two ribs)may be used in a mirror-image cylinder head housing of an internal combustion engine having its cylinders arranged in a V-configuration. With this arrangement, one of the ribs or projections on one thrust stopper may be used to orient a first rocker arm shaft in one cylinder head housing and another rib or projection of another thrust stopper may be used to orient a second rocker arm shaft in the opposing cylinder head housing. In this manner, one projection or rib on each thrust stopper is non-functional, provided that only one rocker arm shaft is provided for each cylinder.
In any engine configuration, once the camshaft has been installed, the thrust stopper is slid into the slot-like receiving opening in the cylinder head housing and into the annular groove of the camshaft. Then, the rocker arm shaft is installed in the correct position in the cylinder head housing.
The present invention is also directed to a cylinder head arrangement for an internal combustion engine. The cylinder head arrangement includes a cylinder head housing and at least one camshaft located within the housing. Each camshaft has at least one cam formed thereon. The cams provide the necessary energy through a valve operating assembly to operate the intake and exhaust valves associated with the internal combustion engine. The cylinder head arrangement may include multiple cylinders or multiple banks of cylinders arranged in various configurations.
Various valve operating assemblies are contemplated to be within the scope of the present invention. For example, at least one rocker arm shaft may be located within the cylinder head housing. Each rocker arm shaft includes at least one rocker arm pivotably mounted thereon having a cam follower located on one end thereof. The cam follower operatively contacts one of the cams to transfer the motion of the cam to operate the required intake valve or exhaust valve. It is also contemplated that the cams on the camshaft may operate a valve operating assembly containing one or more hydraulic linkages. The hydraulic linkages transfer the motion of the cam to operate the required intake valve or exhaust valve. It is also contemplated that the valve operating assembly may be omitted. With this arrangement, the cams directly act upon the intake valve or exhaust valve to operate valves at predetermined times.
In accordance with the present invention, the cylinder head arrangement further includes a thrust stopper positioned within a receiving opening in the cylinder head housing. The thrust stopper includes a first orienting assembly for orienting the camshaft in a predetermined camshaft orientation within the cylinder head housing. The first orienting assembly prevents incorrect installation and axial movement of the camshaft along the camshaft axis within the cylinder head housing.
In accordance with the present invention, the cylinder head housing may include at least one dismantling recess located adjacent the receiving opening for the thrust stopper to permit access to the thrust stopper, which permits removal of the thrust stopper during a maintenance operation.
The cylinder head arrangement may further include a valve cover assembly secured to the cylinder head housing. It is contemplated that at least a portion of the valve cover assembly overlies the thrust stopper. The valve cover assembly prevents removal of the thrust stopper when installed.
The cylinder head arrangement may further include a sealing assembly positioned between the valve cover assembly and the cylinder head housing. At least a portion of the sealing assembly is positioned between the thrust stopper and the valve cover assembly. The sealing assembly reduces any clatter or movement of the thrust stopper within the receiving opening in the cylinder head housing. Clatter occurs when the thrust stopper vibrates within the receiving opening and periodically contacts the surrounding engine components and/or cylinder head housing.